If I understand your question , you are asking how to “optimise” your website more than marketing it , anycase let me break this in 2 part, optimize and than market.Evidently like be below have mentioned , we assume its an eCommerce store and also you are not really having the 2Lakh page but its a CMS ecommerce platform.If for any reason the above 2 assumptions are not valid, than i think you have a large complex and manual project/process in hand.
To optimize for performance , in a typical ecommerce site all product pages and many other pages as well, will be rendered from db , so below are some points
global image compression must be setup at the platform level
all style and scripts consolidated and minified
the above two should take care of must of the performance
please ensure you dont have any complex URL redirections or zoning this will kill
Next is the 3 important items in optimisation,
-> Crawling : Google webmaster needs to index your main site URL
-> Product feed : For all product pages you will need to publish them on merchant console (you dont need to really index them on webmaster for each product)
-> Sitemap : Ensure sitemap is structured for main pages and while product pages should not be robot restricted , it need not be on the sitemap per say.
Well the above is written with some assumptions and also from my extensive experience dealing with many eCommerce and large site.
I may have (surely) missed a few items but the above should cover the most important ones for starters. All the best.